The main stream brassiere wire of today has a resin protective cap 2 attached to the tip of wire 1 as illustrated in FIG. 1 to prevent the metal wire from projecting through a fabric casing or to improve the wearer's comfort. There are several methods of attaching protective cap 2 ranging from a simple insertion of protective cap 2 to insert-molding of the wire with protective cap 2.
The major problem of the wire having a protective cap is that the protective cap detaches from the wire during wearing or washing. In order to overcome this problem, wire suppliers provide means to make the protective cap hard to detach from the wire by forming a hole or notch at the tip of the wire as disclosed in U.S. Pat. No. 4,133,316. As a result, the protective cap with a hole or notch is less likely to detach from the wire than the one without a hole or notch; this does not mean that the protective cap with a hole or notch never detaches from the wire.
On the contrary, the presence of a hole or notch formed at the wire tip increases a hazard when the protective cap detaches. For this reason, it is desirable to enhance the holding strength of the protective cap without forming a hole or notch at the wire tip portion.
More particularly, as illustrated in FIGS. 2a and 2b, the conventional method involves the formation of notches or the like at the tip of wire 1a and the formation of a hole on protective cap 2a at the point which corresponds to the notch so as to mate and secure the protective cap 2a on wire 1a. 
However, protective cap 2a is hard to attach unless the size of the hole on the protective cap and that of the wire hook portion have some tolerance. As a result, the wire hook portion has too much play. This weakens the holding strength, causing a detachment of the protective cap during wearing or washing. In addition, the area on the protective cap in which a hole is formed provides much poorer strength than other areas. As a result, the protective cap often disintegrates from the hole thereof during washing.
Hence, in the past, instead of separately molding a protective cap and attaching it to the wire, the insert-molding method was devised as disclosed in U.S. Pat. Nos. 4,306,565 and 5,934,970. This insert-molding of a protective cap enhanced the adherence between the wire and the protective cap, thereby reducing the chance of disintegration during washing.
Nevertheless, the protective cap had a poor holding capacity unless a notch or hole was formed on wire body 1b and a hook was made as illustrated in FIGS. 3a and 3b. Furthermore, this wire insert-molding had a characteristic that both ends were covered with a resin. As a result, a continuous molding used for electronic components and the like could not be adopted for production of protective caps, entailing poor productivity.